Periodic Table

Chapter 6

Periodic Table

Many different versions of the Periodic Table exist

All try to arrange the known elements into an organized table

Alternate Periodic Tables

Alternate Periodic Tables

Alternate Periodic Tables

Alternate Periodic Tables

Alternate Periodic Tables

Alternate Periodic Tables

Alternate Periodic Tables

Elements known since Ancient times

Elements Discovered in 1600’s

Elements Discovered in 1700’s

Elements Discovered 1800-1810

Elements Discovered 1810-1863

Elements Discovered 1875-1899

Elements Discovered 1900-1940

Elements Discovered 1944-1961

Elements Discovered 1966-1996

Elements Discovered since1999

History

1869 - Russian chemist and teacher, Dmitri Mendeleev proposed a table for organizing elements

Mendeleev arranged the elements in a table based on increasing atomic mass.

History

Mendeleev placed elements next to each other with similar chemical properties

He would leave elements out of order based on atomic mass if they lined up better based on chemical properties

History

Mendeleev left spaces for elements not yet discovered– He predicted properties of elements that would fit

in those spots

He predicted very closely the properties of Ge, Ga, Sc, and 5 others

History

1913 - British physicist, Henry Moseley, determined the atomic numbers for the elements

The modern periodic table is arranged in order of increasing atomic number.

Periodic Table

Arrangement

Columns are called Groups– Numbered 1-18

Rows are called Periods

Elements in the same group have similar properties

Group Names

Group 1 - Alkali Metals

Group 2 - Alkaline earth metals

Group 17 - Halogens

Group 18 - Inert or Noble gases.

Group Names

Groups 3-11 – Transition Metals

Bottom 2 rows – Inner Transition

Phases at STP

Most elements are solids at STP

Hg and Br are liquids at STP

H, N, O, F, Cl and Noble Gases are all gases at STP

Periodic Law

Periodic Law – When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

Valence Electrons

Electrons in outermost occupied energy level

Valence Electrons are responsible for most chemical properties– Elements in the same group have similar

properties because they have the same number of valence electrons

Classifying Elements

Elements are classified into 3 groups based on their properties:

Metals – Left and Middle

Nonmetals – Right

Metalloids - Staircase

Metals

Good conductors of heat and electrical current

High luster or sheen Many are ductile, meaning they can be

drawn into wires Most are malleable, meaning they can be

hammered into thin sheets

Metals

Metallic Character increases as you move towards the lower left

Most Metallic Element is Francium, Fr

Nonmetals

Most are gases at room temperature, some are solids, and one is liquid

Most are poor conductors

Most solids are brittle

Nonmetals

Non-Metallic Character increases as you move towards upper right

Most nonmetallic element is Fluorine, F

Metalloids

B, Si, Ge, As, Sb, Te

Have properties of both metals and nonmetals, based on conditions

Exceptions:– Al and Po are metals– At is a nonmetal

Group Characteristics

Alkali Metals (Group 1)– H, Li, Na, K, Rb, Cs, Fr– All have 1 valence electron, tend to form +1 ions– Most reactive metals– Not found in nature by themselves, always

combined with someone else– Have properties of metals but are softer and less

dense

Group Characteristics (cont)

Alkaline Earth Metals (Group 2)– Be, Mg, Ca, Sr, Ba, Ra– All have 2 valence electrons, tend to form +2 ions– Harder and more dense than alkali metals, but

also have higher melting and boiling points– Highly reactive, but not as much as alkali metals– Not found by themselves in nature

Group Characteristics (cont)

Halogens (Group 17)– F, Cl, Br, I, At– All have 7 valence electrons, tend to form -1 ions– Strongly non-metallic– Most active nonmetals– Have low melting and boiling points– Combine readily with metals to form salts

Group Characteristics (cont)

Noble Gases (Group 18)– He, Ne, Ar, Kr, Xe, Rn– Colorless gases that are extremely non-reactive– Full valence shell, non-reactive– All are found in small amounts in our atmosphere

Group Characteristics (cont)

Transition Metals (Groups 3-11)– Most are excellent heat and electrical conductors– Most have high melting points and are hard,

except Hg– Less active than group 1 and 2 metals– Many combine with Oxygen to form oxides

(Chemical property)– Many have more than one oxidation number– Form compounds that are colorful

Reminder

STP Standard Temperature and Pressure

– 1 atm, 0°C

Reference Point for most measurements

Diatomics

Eight elements are diatomic molecules when alone in nature (exist as two atoms bonded together)

H2, N2, O2, F2, Cl2, Br2, I2, At2

Diatomics

Hydrogen and the Magic 7

Coloring

Color in the specific groups with your own color choices

Coloring

Color in the different classifications with your own color choices

Metals, Nonmetals, Metalloids

Orbital Blocks

s - block

p - block

d - block

f - block

Periodic Trends

How a property changes either across a period or down a group– Atomic Number– Atomic Mass– Atomic Radius– Ionic Radius– Ionization Energy– Electronegativity

Trends

Atomic number increases across a period.– Increasing number of protons

Atomic number increases down a group– Increasing number of protons

Trends

Atomic mass generally increases across a period.– Increasing protons, neutrons, and electrons.

Atomic mass increases down a group.– Increasing protons, neutrons, and electrons.

Radius

Atomic Radius – measure of the size of the atom– Half the distance between two nuclei

Ionic Radius – measure of the size of an ion

Trends

Atomic Radius decreases across a period– More protons to pull on the electrons

Atomic Radius increases down a group– Increasing electrons into more energy levels

(more shells)

Ions

Atom, or group of atoms, that has gained or lost electrons

Cation – positive ion Anion – negative ion

Ions

When an atom loses an electron, it becomes positively charged– The radius becomes smaller– Metals tend to lose electrons

Ions

When an atom gains an electron, it becomes negatively charged– The radius becomes larger– Nonmetals tend to gain electrons

Trends

Ionic Radius decreases for positive ions across a period– More protons to pull on the electrons

Ionic Radius decreases for negative ions across a period– More protons to pull on the electrons

Ionic Radius

+1 +2 +3 +4 -3 -2 -1

Trends

Ionic Radius increases down a group– Increasing electrons into more energy levels

(more shells)

Ionization Energy (IE)

Amount of energy required to remove an electron from an atom– Ca Ca+ + e- 590kJ/mol

First ionization energy is removing the first electron

Second Ionization energy is removing the second electron after having the first removed– Ca+ Ca2+ + e- 1145kJ/mol

IE Trends

Ionization energy tends to increase across a period– More protons are able to hold on tighter to

electrons

Ionization energy tends to decrease down a group– Electrons are farther away from the protons (more

shells)

Electronegativity (EN)

Ability of an atom to attract an electron from another atom when in a compound. – Noble gases are usually omitted since they don’t

form compounds– Fluorine, F, is the most electronegative element

with a value of 4.0– Francium, Fr, is the least electronegative element

with a value of 0.7

EN Trends

Electronegativity tends to increase across a period– More protons are able to attract electrons better

Electronegativity tends to decrease down a group– Electrons are farther away from the protons (more

shells)

Trends Summary

Property Period (LR) Group (TB)

Atomic Number

Atomic Mass

Atomic Radius

Ionic Radius

Ionization Energy

Electronegativity

Reactivity

Elements that are more reactive tend to either gain or lose electrons very easily

Elements that lose electrons easily have low IE and low EN– Lower left, Fr

Elements that gain electrons easily have high IE and high EN– Upper right, F